Breastmilk pumps are well known, and are generally comprised of a hood that fits over the breast, a vacuum pump connected to the hood for generating an intermittent vacuum within the hood, and a receptacle for the expressed milk. Manually driven vacuum pumps as well as those that are driven by a motor are ordinarily used. The vacuum pumps of these devices, as a rule, intermittently generate a vacuum or negative pressure within the hood, with the hood encompassing the nipple and a substantial amount of the breast. The intermittent suction action of the pumps serves to pull on the breast and thereby extract milk in an action reminiscent of suckling. The milk so extracted typically flows from the hood into a collection container for storage and later use.
Apart from the purely hygienic requirements for such equipment, there also exist technical problems which are at least insufficiently solved with regard to prior art devices. One such significant failing of nearly all of the prior art devices is that the milk expressed often reaches the vacuum line or even the pump. In order to eliminate such a serious problem, many prior devices contain so-called safety volumes between the hood and the pump. Such a solution of the problem is expensive and usually cannot provide effective protection of the vacuum line and pump from milk. Also, varying degrees of vacuum can be generated as the milk receptacle fills, which must then be compensated for.
Another important consideration in the design of a breastpump is the vacuum created by the pump and its effect upon the breast. While it is the ultimate desire to design a breastpump that perfectly duplicates a baby's nursing action, this is extremely difficult to achieve. However, there are several important characteristics that a breastpump, properly designed, can simulate. Three things about the vacuum and its application to the breast are considered very important. These are: (a) how much vacuum does a pump create on the breast; (b) how long is that vacuum applied to the breast; and (c) can the vacuum be regulated within safe, natural limits to suit the mother's comfort with proper expression of milk?
First, a vacuum that is much greater than that "vacuum" created by a suckling baby is not only unnatural, it can also cause pain and injury to the breast. Second, just as too much vacuum can hurt the breast, too long an application of vacuum is also unnatural, and may create discomfort and injury. Third, uncontrollable vacuum--either vacuum in excess of safe, natural limits or vacuum that cannot be finetuned for a woman's comfort--makes a breastpump less effective or even useless.
In utilizing breastpumps, whether they are of a motor driven or manually driven type, it has been found that the wide variety in the size of breasts also gives rise to problems if a single breastpump is to be given universal application. This is particularly true in regard to smaller breasts, since the hoods used by most breastpumps are designed to handle a medium or larger-size breast. For example, the small breast can be sucked into a standard size hood to an extent that, if not necessarily painful, is at least rather uncomfortable. In general, the funnel of such a suction hood should abut the breast at a distance from the nipple that is as large as possible, which condition demands a funnel for the hood which is also as large as possible. While it has become obvious that the provision of different suction hoods having various funnel diameters solves such a problem, it does so in an unsatisfactory way, since providing a product line of different size hoods is expensive from a marketing and manufacturing standpoint.